Process for refining ester type oils, fats, and waxes



- Patented Jan. 7, 19 41 UNITED STATES PATENT 'OFFICE' rnocn'ss FOR nnrnvmc ESTER. TYPE OILS,

- m'rs. AND WAXES Hendrik Berend Johannes Schurink, The Hague, and Willem Ooltof, Amsterdam, Netherlands, assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 25, 1938, Serial No. 215,852. In. the Netherlands July 2, 1937 8 Claims. (01. 260-425) ticularly adapted for the quantitive selective removal ofsaid impurities. Another object of our invention is the efilcient and economical refining of ester type oils without material loss of valuable components thereof. A further object is to provide a fatty oil extraction process which involves little or noloss of refining agents.

Fatty oils and the like are very complex mixtures and the impurities which must be removed therefrom in order to produce a commercially ac- 20 ceptable product are not only numerous but also extremely diverse in nature. Acids, coloring constituents, albumens, malodorous substances and other undesirable impurities must be thoroughly removed without sacrificing any of the valuable esters which themselves are a mixture of compounds of varying properties, particularly varying solubilities. None of the extracting agents which have been previously su gested for the refining of ester type oils is perfectly suited to the selective separation of the undesirable from the desirable components of these complex mixtures without loss. We have folmd that the very exacting requirements for such selective separation are much better met by imines when applied under the proper circumstances.

Imines, being in general miscible with ester type oils, cannot serve as extracting agents by themselves. We have discovered, however, that by the addition of suitable substances which are miscible with the imines, but immiscible, or miscible to a very limited extent only, with the fatty esters to be refined, such as water, ethanol or the like, imine mixtures may be formed which are eminently suitable for refining ester type oils, fats and waxes. These new fatty oil refining agents have a unique combination of chemical and physical properties which especially adapts them to 50 the selective removal of all the many diiierent type oils, fats and waxes, which solvents are parcompounds occurring as impurities in animal and vegetable oils without substantially removing valuable ester components. These solvent mixtures have the following further advantages:

(1) They do not, or only to a very slight extent.

emulsify the fatty materials being refined;

(2) They practically do not saponify the desirable ester components of fatty oils and the l (3) They form imine soluble soaps with free fatty acids, which soaps are not subject to the splitting oil of water with formation of imides, to any substantial extent.

As a result of the low solubility of fatty acid glycerides in the extracting agents used in the process ofour invention, and the absence of emulsification and saponiflcation difficulties, there is only a very slight, if any, loss of valuable material in our refining process. Furthermore, the ease of separation of extract and rafilnate resulting from the absence of emulsification, together with the freedom from undesirable side reactions of the imine fatty acid soaps, results in only small losses of extracting agent in the refining and solvent recovery steps of the process of our invention.

The imines which are used in the process of our invention are compounds having an imino.

group the nitrogen atom of which is joined to one aliphatic carbon atom or to two different carbon atoms in an aliphatic chain. Typical examples of imines coming into consideration are especially the alkene imines such as ethylene imine (esp 0m) 1-2 pr'opene-imine, 1-3 propene imine, tetramethylene imine, alpha and/or beta methyl-tetramethylene imine, piperidine, pyroline, morpholine, and the like, as well as imines containing the aliphatic group 7 a such as 1 (ortho-hydroxy-phenyl) 1 imino ethane and the like. These imines or suitable'substitution products thereof may be used individually or as mixtures of group members, with or without other suitable compounds which may be solvents for one or more components of the'material being refined, as with ammonia or alkylolamines, etc., or which may behave solely'as diluents.

Because of its cheapness we generally prefer to employ water as the agent for rendering the chosen imine extracting agent-immiscible with the fatty material being refined as recovery of the solvent is thereby simplified since only prevention of loss of imine is necessary. In certain cases it is advantageous to use other oxy. compounds such, for example, as water soluble alcohols or ketones or the like, such asmethyl, ethyl, isopropyl and tertiary butyl alcohols, or acetone, etc. i

The amount of imine used and the proportion of miscibility reducing agent,v employed may be varied widely in the process of our invention, the choice in any particular case being influenced by the costs of handling and of recovering the solvent as balanced against the degree of refining achieved. Usually only small amounts of water are required to render imines sufiioiently immiscible with the fatty oil being treated so that satisfactory refining may be successfully carried out. About 10% to about 75% of the weight of the chosen imine may be used for example. Where other liquid oxy compounds are used in place of water somewhat larger amounts may be required.-

It is sometimes desirable to use a mixture of miscibility reducing agents'such for example as an aqueous alcohol solution or a mixture of alcohols and/or ketones, or the like.

Dependent on the nature of the fatty material to be refined and the imine containing refining agent chosen, the extraction may be carried out at ordinary, reduced or elevated temperatures, altho temperatures below about 100 C. are preferred. The refining may be effected batchwise, intermittently or continuously. Countercurrent extraction may be advantageously used and the imine extraction may be preceded and/or followed by treatment with other suitable solvents. The fats, oil or waxes may, where desirable, be first taken up in a suitablesolvent or dispersing agent.

One simple method of carrying out the process of our invention comprises, for example, adding a quantity of the chosen imine to the fatty material to be refined, then adding sufiicient water, for example, to cause the separation of a phase containing the greater part of the imine. The mixture is then mixed mechanically to insure intimate contact of the phases after which the phases are separated by stratification and decantation or by centrifuging or the like. After the extraction, the raiiinate phase may be freed of any refining agent and extract components remaining therein by washing with water, alcohol or the like, or vacuum or steam distillation or blowing with an'inert gas or other suitable methods may be used for removing the last traces of imines and/or other components of the refining agent used.

The imine may be recovered from the extract phase by chemical means, e. g. with the aid of alkalis or of mineral acid, or by physical means such as distillation of the diluted or undiluted extract. Recovery by distillation is especially advantageous for the preferred lower boiling imines. The distillation may be carried out under normal or reduced pressure and may be ordinary or flash distillation in the presence or absence of steam. Where an alcohol or the like is used to render the imine immiscible with the fatty oil, the alcohol may be recovered in the same or in a separate distillation.

For the purpose of making our invention more clear, the following typical examples are given showing its application to the refining of cocoa butter. It will be understood, however, that these are intended as illustrations only and imply no limitation on our process which is equally applicable to the refining of a wide variety of other ester-type oils, fats and waxes including, for example, cotton seed oil, palm oil, olive oil, train oil, cocoa fat, soy bean oil, sardine oil and the Y like.

Example I 50 g. cocoa butter, acid figure 7.8, is intensively mixed at 50 C. with a mixture of 5 g. ethylene imine and 2 g. water. The mixture is subsequently centrifuged; the oil layer is washed and dried. The acid figure of the refined cocoa butter is 0.28.

Example II 50 g. cocoa butter, acid figure 7.8, is shaken at 60 C. for 20 minutes with a mixture of 5.3 g. of the compound (If-CH: NH

14.9 g. ethanol (of 100% concentration) and 1.4 g. water, which mixture is a homogeneous liquid at temperatures above 40 C. The extract layer (top layer) is subsequently separated off by centrifugation, whereupon the oil is washed with ethanol and water, until it reacts neutrally to bromine cresol purple. The refined cocoa butter has an excellent color, smell and taste,-and has an acid figure of only 0.17.

Example III 50 g. cocoa butter, acid figure 7.8, is shaken at 60 C. for 20 minutes with a mixture of 6.3 g. piperidine and 2 g. water. The mixture is then centrifuged, the extract layer (bottom layer) being separated oil. The oil is washed consecutively with alcohol-containing water and with pure I water until it reacts neutrally. The acid figure of the refined cocoa butter is 0.21.

These examples show clearly that our refining agents are exceptionally efiective in the removal of all types of impurities from ester-type oils, fats and waxes. This high degree of refining is accomplished in a most economical manner by the process of our invention as a result of the ease and completeness of recovery of both refining agent and refined oil, compared with prior methods.

It will thus be evident that our invention offers many advantages. It is capable of many modifications both with respect to the animal and vegetable oil, fats and waxes which may be treated and the solvent mixtures which may be used for the extraction. It is highly flexible in regard to the conditions of extraction and recovery of solvent and reilned product. Our invention is therefore not to be regarded as limited to the details disclosed by way of illustration nor by the theories advanced in explanation of the improved results attained, butcnly by the terms of the accompanying claims in which it is our intention to claim all novelty inherent therein as broadly as possible in view of the prior art.

We claim as our invention: I

1. In a process of purifying a substance of the class consisting of oils, fats and waxes of the ester type, the step which comprises contacting said and aqueous ethanol.

2. In a process of purifying a substance of the class consisting of oils, fats and waxes of the ester type, the step which comprises contacting said substance with a mixture of ethylene imine and water at a temperature below about 100 C.

3. In a process of purifying a substance of the class consisting of oils, fats and waxes of the ester type, the step which. comprises contacting said substance with a liquid mixture of an imine of the formula where R and R may be the same or dliferent alkyl, aralkyl or aryl groups and water.

4. In a process of purifying a substance of the class consisting of oils, fats and waxes of the ester type, the .step which comprises contacting said substance with a liquid mixture of an unsaturated aliphatic imine and a member of the class con-'1 sisting ofwater and water soluble simple alcohols and simple ketones which mixture is incompletely miscible with said substance.

5. In a process of purifying a substance of th class consisting of oils, fats and waxes oi the ester type. the step which comprises contacting said substance with'a liquid mixture of an aliphatic imine in which the nitrogen is linked directly by two of its bonds to a divalent aliphatic'chain and a water soluble liquid hydroxy extraction agent for said ester type substance miscible but nonreactive with said imine which mixture is incompletely miscible with said substance.

6. In a process of purifying a substance of the class consisting of oils, fats and waxes of the ester type, the step which comprises extracting impurities from said substance with a liquid mixture of a (a a a-t-;( t ---t'-a where the R's may represent hydrogen or the same or different alkyl, aralkyl or aryl groups and n is an integer which may be zero and a water solua water soluble extracting agent for said ester type oils, fats and waxes which is miscible and nonreactive with said imine to cause formation of two liquid layers.

HENDRIK BEREND JOHANNESBCHURINK. WILLEM COLTOF. 

